This is one of my favorite paintings, "Saint Matthew and the Angel", by Guido Reni, 1597. I can't recall where I read the commentary on it most recently, but it mentioned how absorbed Matthew's appearance is in listening to the angel transmit the words of God.
Great Saint Matthew, Pray for us!
"Jesus saw a man called Matthew sitting at the tax office, and he said to him: Follow me." Jesus saw Matthew, not merely in the usual sense, but more significantly with his merciful understanding of men."
He saw the tax collector and, because he saw him through the eyes of mercy and chose him, he said to him: "Follow me." This following meant imitating the pattern of his life - not just walking after him. Saint John tells us: "Whoever says he abides in Christ ought to walk in the same way in which he walked."
"And he rose and followed him." There is no reason for surprise that the tax collector abandoned earthly wealth as soon as the Lord commanded him. Nor should one be amazed that neglecting his wealth, he joined a band of men whose leader had, on Matthew's assessment, no riches at all. Our Lord summoned Matthew by speaking to him in words. By an invisible, interior impulse flooding his mind with the light of grace, he instructed him to walk in his footsteps. In this way Matthew could understand that Christ, who was summoning him away from earthly possessions, had incorruptible treasures of heaven in his gift.
(from a homily by Saint Bede the Venerable)